Be aware that most rigid tapping setups require an encoder that is 1:1 geared to the spindle and has an index pulse. For many machines that can be a problem.

It still seems to be on trend to try to use servo drives on the spindle. However, most controllers are expecting to see a VFD in that position, so control of direction and speed control needs to be considered.

Although rigid tapping seems like a rite of passage, a tension-compression head has a lot to recommend it. You simply need to achieve reasonable speed control in order to synchronise the Z axis feed to the thread pitch. Just saying.